A polyurethane film has excellent stretchability, for example, has a strength equal to rubber despite being thinner and lighter than rubber, and has high wear resistance, and is excellent in weather resistance and oil resistance compared with rubber. Therefore, the polyurethane film is slit into a tape shape and used for a fastening part at the end of underwear, undergarments, sportswear, such as swimwear and leotards, T-shirts, polo shirts and the like or widely used for inner garments, outer garments, sports garments, garment materials and the like as a reinforcement of cloth for the purpose of suppressing droop of the clothing fabric in place of a cotton or braided tape.
On the other hand, a heat adherent film is slit into a tape shape and used for bonding fabrics together for hemming trousers or for preventing intrusion of rainwater through the sewn part by heat-bonding the tape from the back side of the seamed portion of a waterproof sewn product. The heat adherent film includes a polyurethane type, a polyamide type, a polyester type, a polyethylene type, an ethylene-vinyl acetate copolymer, an ethylene-ethyl acrylate copolymer, an ethylene-atactic polypropylene copolymer, a polyvinyl chloride type, a polyvinyl acetate type, an acryl type and the like, but a polyurethane-type film is excellent in terms of maintaining stretchability, cold resistance, water resistance and soft texture in the vicinity of the seam.
However, more improvements are being demanded for various elastic functions of the heat adherent film. For example, when a heat adherent tape is used for fray prevention in a fastening part at the end of underwear, undergarments, sportswear, such as swimwear and leotards, T-shirts, polo shirts and the like, the fastening force is insufficient due to a small kickback force of the tape. When a high-power tape is used for strengthening the fastening, a hard fabric may result, i.e., it is necessary to have heat adhesion, and elastic functions, be reduced in stress to deformation strain and in the hysteresis loss of stress at expansion and contraction.
A polyether is often used as the soft segment component of a polyurethane resin. Above all, a polyurethane resin using polytetramethylene ether glycol (hereinafter simply referred to as PTMG) which is a polymer of tetrahydrofuran (hereinafter simply referred to as THF) is excellent in the elastic property, low-temperature property, hydrolysis resistance and the like and therefore, is being used in various fields. However, a tape obtained from the polyurethane resin using PTMG is reduced in the elastic functions resulting from crystallization of the soft segment at the stretching. When the polyurethane tape using PTMG is designed as a polymer having a low melting point so as to ensure heat adhesion, this incurs great reduction in the elastic performance of the film.
For the purpose of improving these elastic functions, various efforts have been made with an attempt to suppress the crystallinity of the soft segment in the polyurethane by using various diols, but there are no publications that describes a polyurethane that has succeeded in enhancing the above-described elastic functions to a sufficiently satisfactory level.
For example, there is a publication describing use of a copolymerization-type polyether polyol as the soft segment of the polyurethane. Patent Document 1 describes a polyether glycol in which 4.2 mol % of a neopentyl glycol group is copolymerized, and Patent Document 2 describes a polyurethane using a 3.4 mol % copolymerized polyether glycol, but these polymers have a low copolymerization ratio and a polyurethane remarkably enhanced in the mechanical property when formed into a tape or film shape, such as strength, elongation and elastic recovery percentage, is not disclosed. Furthermore, Patent Document 3 describes a polyurethane using a copolymerized polyol of THF and 3-alkyl tetrahydrofuran but is silent about the hysteresis in the expansion and contraction, and Patent Document 4 describes improvement of elastic functions of a copolymerized polyurethane containing from 8 to 85 mol % of neopentyl glycol group and/or 3-methyl-1,5-pentanediol; however, a thermoplastic polyurethane and heat adhesion are not disclosed.    [Patent Document 1] Japanese Unexamined Patent Publication (Kokai) No. 61-120830    [Patent Document 2] U.S. Pat. No. 4,658,065    [Patent Document 3] Kokai No. 5-239177    [Patent Document 4] Kokai No. 2-49022